It all depends on what script(s) you are using in your members area. I personally do everything with Notepad and Wordpad, with Find/Replace and Copy/Paste it isn't hard at all to add, change, or remove content.
It really depends on how cleanly you setup the site. If pictures are in uniform directories with uniform names (ex: c1.jpg-c50.jpg in directory name1/ c51.jpg-c100.jpg in directory name2) It's always pretty easy to manually update anything.

I can't think of a lot of pro's or con's to doing it either way, it really is a matter of personal preference. It all depends on your design skills, but sites I code by hand come out looking a lot more personal and unique than script produced sites, and there are more opportunities to tweak html, alt tags, etc for SEO. (or are you using scripts for that too?)

The only script i've come across that could make me switch is PHPNuke. I think if a dedicated webmaster found a seemless way to integrate a members/guest setup with PHPNuke on a porn site it would be revolutionary. No more ill-concieved "glossy tours", people can see what they are getting from the main page, and are just restricted to what they can or can't do/see until they join. In my mind that is absolutely the way adult sites should be; WYSIWIG from page one.

If I had hosting that supported PHP i'd already be using it. It allows for the simple integration of member signup/login, HUGE movie/photo galleries, member uploads, message board, polls, detailed stats for admin, news/updates post, tons of other shit I can't think of. It comes with these features standard, and hundreds more that do anything and everything are available as plug-ins. It's basicly an all in one members only site script that is so extremely customizable you won't feel like the site was spit out by a script.

For a somewhat decent example of what someone has done to use a portal script (PHPNuke in this case) to create a good WYSIWIG adult site check out:
http://www.livecamboy.com